A diaphragm pressure sensor configured to convert flexure (displacement) of a diaphragm pressurized by a fluid into an electric signal and to detect a pressure change based on this electric signal has been conventionally proposed as one of pressure sensors capable of detecting a pressure change of a fluid such as a liquid or a gas (see Japanese Patent Laid-Open Publication No. Hei 11-44597, for example).
However, such a diaphragm pressure sensor is configured to detect pressure by use of the flexure of the diaphragm. Accordingly, the diaphragm pressure sensor has problems that a relatively long time period is required for detection, and that it is difficult to achieve measurement at high accuracy because the displacement of the diaphragm generally shows a non-linear characteristic.
In recent years, a pressure sensor applying a magnetostrictor is drawing attention as a measure for solving these problems. The pressure sensor applying a magnetostrictor utilizes a characteristic of the magnetostrictor that causes a large change in magnetic susceptibility upon application of external stress. Such a pressure sensor is applied to the field of tire pressure detection devices (see Japanese Patent Laid-Open Publication No. Hei 11-287725), for example.
As shown in FIG. 5, a pressure sensor 1 applied to this tire pressure detection device is configured to apply a compressive force caused by internal pressure of a tire to a giant magnetostrictive material 3 via a push rod 2. Moreover, a coil 4 disposed around this giant magnetostrictive material 3 detects a change in magnetic susceptibility of the giant magnetostrictive material 3 and thereby the device measures air pressure in the tire.
However, this publicly known conventional pressure sensor 1 is configured to apply the air pressure of the tire being the measuring object to the giant magnetostrictive material 3 via the push rod 2, and therefore has problems of a difficulty to detect a small change of the air pressure, and of reduction in sensitivity and accuracy of pressure measurement.
Moreover, the giant magnetostrictive material 3 is made of a bar member, and is configured to receive the compressive force from the push rod 2 only by use of an end face in an axial direction thereof. Accordingly, there is a problem that the compressive force of this push rod 2 acts on a small area and an amount of deformation (the change in magnetic susceptibility) of the giant magnetostrictive material 3 is therefore small.